SYNTHETIC STUDIES TOWARDS PRISMANES - SECO-(6)-PRISMANE

The first synthesis of seco-[6]-prismane 5, the closest, one-bond-away secologue of [6]-prismane 4, from the readily available Diels-Alder adduct of 1,5-cyclooctadiene and dimethoxytetrachlorocyclopentadiene is described. The key chemical operations in the 17 step sequence are (i) 4+2-cycloaddition of singlet oxygen 20 --> 22, (ii) boron mediated fragmentation 47 --> 14 and (iii) intramolecular 2+2-photocycloaddition 14 --> 49. The methodology outlined here offers opportunities for further elaboration to [6]-prismane as well as several of its homo- and secologues.